One of the principle sources of parasitic losses, complications and bulk in an internal combustion engine has to do with the waste heat generated by the internal combustion engine process. Attempts have been made to manage heat flux from the material surrounding combustion chambers by paying careful attention to flow passages, coolant flow rates and temperatures through such passages. Typically the internal combustion engines are liquid cooled so as to maximize the heat flux to the cooling system, particularly in the region closely adjacent the combustion chamber. When cooling systems operate under off design conditions because of duty cycle or component malfunction, it can lead to a condition of uncontrolled boiling in the coolant passages for the engine. This condition causes complete loss of liquid to metal contact and drastically reduces the heat flux carried away by the cooling system. When this is left uncontrolled, the pressure relief for the system, usually a radiator cap, is opened to release pressure and allow even greater generation of steam. This, in turn, has a potentially catastrophic affect on the temperature of the internal metal parts of the engine.
There is, however, a condition between normal liquid flow conditions and uncontrolled boiling that provides an optimum heat flux from the parts to be cooled by the liquid cooling system. This is known as nucleate boiling in which bubbles are generated on a microscopic scale. This allows significant increases in heat flux, but this condition, at best, is a momentary transition between sub-boiling conditions and uncontrolled or macro-boiling.
What is needed in the art therefore is a cooling system which effectively maintains nucleate boiling in an engine cooling system to maximize heat flux from the engine combustion chamber.